This invention introduces a MEMS capacitive platform that cancels bias-induced stiffening with co-planar “repulsive” electrodes, boosting displacement response by over 6× without increasing noise, enabling simpler, smaller, and more sensitive microphones and sensors.
Background: Capacitive MEMS sensors and actuators require a DC bias for operation, but this bias inadvertently stiffens the movable element, raising resonance, narrowing bandwidth, and reducing sensitivity. Existing fixes include multilayer stacks, sacrificial layers, or closed-loop feedback, but these add cost, parasitics, and noise, while tighter gap tolerances increase pull-in risks. The result is a persistent trade-off between sensitivity, manufacturability, and device stability that limits next-generation MEMS performance.
Technology Overview: This invention patterns interdigitated comb electrodes and a suspended beam in a single conductive silicon layer on an SOI wafer. Two lower-voltage “attractive” electrodes supply sensing bias, while higher-voltage “repulsive” side electrodes generate an opposing electrostatic force. The grounded bulk silicon shapes the fields to create a net negative electrostatic spring that reduces natural frequency and amplifies motion. Capacitive readout confirms a >1200% displacement gain and ~35% resonance reduction, achieved using standard planar lithography without sacrificial layers.
Advantages: • >6× sensitivity boost without added thermal noise • Resilient to pull-in, enabling higher usable bias and wider dynamic range • Single-layer SOI process lowers fabrication cost and complexity • Electrically tunable stiffness allows on-demand bandwidth/gain control • Reduced parasitics vs. multilayer designs, improving SNR and stability • Compact CMOS-compatible layout simplifies integration and packaging
Applications: • High-fidelity MEMS microphones for consumer and professional audio • Low-noise accelerometers and gyroscopes for automotive and IoT systems • Barometric and differential pressure sensors with higher resolution • Micro-robotic actuators and micro-pumps with greater displacement per volt • Lab-on-chip valves and ultrasound transducers requiring enhanced sensitivity
Intellectual Property Summary: • US Provisional Patent Application 63/751,591 – Filed January 30, 2025
Stage of Development: Lab validated – Prototype testing demonstrated >1200% displacement gain and ~35% resonance reduction under controlled conditions. TRL ~4.
Licensing Status: This technology is available for licensing.
Licensing Potential: Well-suited for MEMS microphone, sensor, and actuator manufacturers seeking scalable, CMOS-compatible designs that deliver greater sensitivity and lower noise without added complexity.
Additional Information: Prototype test data, MEMS process flow details, and performance characterization available upon request.
Inventors: Ronald Miles, Weili Cui, Johar Pourghader